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Transcript of Stack Design Done by Eng. Mohamed AbdElRhaman. Content Definition of the stack Applications of stack...
![Page 1: Stack Design Done by Eng. Mohamed AbdElRhaman. Content Definition of the stack Applications of stack Dispersion Model Selection of stack design Conclusion.](https://reader035.fdocuments.us/reader035/viewer/2022081506/56649e4c5503460f94b4146a/html5/thumbnails/1.jpg)
Stack Design
Done by
Eng. Mohamed AbdElRhaman
![Page 2: Stack Design Done by Eng. Mohamed AbdElRhaman. Content Definition of the stack Applications of stack Dispersion Model Selection of stack design Conclusion.](https://reader035.fdocuments.us/reader035/viewer/2022081506/56649e4c5503460f94b4146a/html5/thumbnails/2.jpg)
Content
• Definition of the stack
• Applications of stack
• Dispersion Model
• Selection of stack design
• Conclusion
![Page 3: Stack Design Done by Eng. Mohamed AbdElRhaman. Content Definition of the stack Applications of stack Dispersion Model Selection of stack design Conclusion.](https://reader035.fdocuments.us/reader035/viewer/2022081506/56649e4c5503460f94b4146a/html5/thumbnails/3.jpg)
Definition
• Stack is a system used in chemical industry that acts as an exhaust to release
gaseous waste streams.
• Stacks are the highest construction in any factory and also higher than the
surrounding buildings
![Page 4: Stack Design Done by Eng. Mohamed AbdElRhaman. Content Definition of the stack Applications of stack Dispersion Model Selection of stack design Conclusion.](https://reader035.fdocuments.us/reader035/viewer/2022081506/56649e4c5503460f94b4146a/html5/thumbnails/4.jpg)
Applications of stack
• Furnaces– Discharge of flue gas
• Absorbers– discharge of clean gas
• Desalination industry– discharge of non-condensable gases
• Wastewater treatment
• Cooling tower in nuclear reactors
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Difference Between Stacks and Flares
• Flares: A control devices that burn hazardous materials to prevent their release into the environment; may operate continuously or intermittently, usually on top of a stack.
• Stacks: only the part that acts as exhaust.
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Dispersion Model
• Dispersion model describes the airborne transport of toxic materials away from the source into the plant or community
• Dispersion model is affected by the followings– Wind speed– Atmospheric stability– Ground conditions (buildings, water, trees)– Height of release (height of the stack)– Momentum and Buoyancy of initial material release
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Dispersion Model
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Dispersion Model
Nomenclature • Ci is the concentration of the chemical species
involved in the model• Ux, Uy and Uz are wind velocities in the x-, y- and
z-directions• Kx, Ky and Kz are diffusion coefficients• Es are the emission sources• ki
1 and ki2 are deposition coefficients (for dry
deposition and wet deposition, respectively)• Q(Ci) represents chemical reactions.• Hr effective height
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Assumptions 1. Steady state conditions2. Uy = Uz = 0 (wind velocity in x-direction only).3. Transport by bulk motion in the x-direction << diffusion in the x-direction (Kx = 0).4. There is no deposition in the system 5. There is no reaction in the system
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![Page 12: Stack Design Done by Eng. Mohamed AbdElRhaman. Content Definition of the stack Applications of stack Dispersion Model Selection of stack design Conclusion.](https://reader035.fdocuments.us/reader035/viewer/2022081506/56649e4c5503460f94b4146a/html5/thumbnails/12.jpg)
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Atmospheric Stability
Surface wind speedDaytime incoming solar radiationNighttime cloud cover
m/smi/hStrongModerateSlight >50% <50%
<2 <5AA – BBEF
2 – 35 – 7A – BBCEF
3 – 57 – 11BB – CCDE
5 – 611 – 13CC – DDDD
>6 >13CDDDD
Note: Class D applies to heavily overcast skies, at any windspeed day or night
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Stability classDefinition
Stability classDefinition
Avery unstableDneutral
BunstableEslightly stable
Cslightly
unstableFstable
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Atmospheric stability
• Dispersion coefficient calculations
Classσy σz
A0.22x(1+0.0001x)-1/20.20x
B0.16x(1+0.0001x)-1/20.12x
C0.11x(1+0.0001x)-1/20.08x(1+0.0002x)-1/2
D0..08x(1+0.0001x)-1/20.06x(1+0.0015x)-1/2
E0.06x(1+0.0001x)-1/20.03x(1+0.0003x)-1/2
F0.04x(1+0.0001x)-1/20.016x(1+0.0001x)-1/2
![Page 17: Stack Design Done by Eng. Mohamed AbdElRhaman. Content Definition of the stack Applications of stack Dispersion Model Selection of stack design Conclusion.](https://reader035.fdocuments.us/reader035/viewer/2022081506/56649e4c5503460f94b4146a/html5/thumbnails/17.jpg)
• (a) NOx and (b) SO2 concentration distributions at ground level. C is in g/m3, w is number of grids in x-direction and m is number of grids in y-direction.
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Selection of stack design
• Design parameters – Stack height (construction parameter)
– Stack diameter (construction parameter)
– Exhaust gas velocity (operating parameter)
– Exhaust gas temperature (operating parameter)
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Effective height Stack height Plume rise
Where Qh is the heat emission form the stack
asph TTcmQ .
Where Ts is the stack gas temperatureTa is the atmospheric temperature
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Conclusion
• The selection of stack design starts by dispersion model.
• Environmental regulation and constrains around the stack controls the concentrations of pollutant and specifies the effective height.
• Stack’s height and diameter are fixed and the control of the effective height happens in the plume rise segment.
• Changing the plume rise height happens by changing the following:– Stack gas exit velocity– Stack gas temperature
![Page 21: Stack Design Done by Eng. Mohamed AbdElRhaman. Content Definition of the stack Applications of stack Dispersion Model Selection of stack design Conclusion.](https://reader035.fdocuments.us/reader035/viewer/2022081506/56649e4c5503460f94b4146a/html5/thumbnails/21.jpg)
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Hr1= 60 m Hr2 = 80 m Hr3 = 100 m
Loading = 1000g/m3Ux = 10 m/sStability class D
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